Received communication signal processing methods and components for wireless communication equipment

ABSTRACT

A method and apparatus for processing received wireless communications are provided. Power delay profiles (PDPs) including PDP elements are processed. Less than half of the PDP elements of each PDP are selected. The selected PDP elements are combined based on position, and the combined PDP elements are qualified for further signal processing to determine a received signal path associated with the PDP.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/845,514 filed Aug. 27, 2007, which is a continuation of U.S. patentapplication Ser. No. 10/794,125 filed Mar. 5, 2004, which issued as U.S.Pat. No. 7,263,376 on Aug. 28, 2007, which claims the benefit of U.S.Provisional Patent Application No. 60/452,484 filed Mar. 5, 2003, U.S.Provisional Patent Application No. 60/452,342 filed Mar. 5, 2003 andU.S. Provisional Patent Application No.60/452,343 filed Mar. 5, 2003,all of which are incorporated by reference as if fully set forth herein.

FIELD OF THE INVENTION

The present invention relates to methods and components for wirelesscommunication equipment and, in particular, methods and components forfacilitating initiation and maintenance of wireless communications.

BACKGROUND

Wireless telecommunication systems are well known in the art. In orderto provide global connectivity for wireless systems, standards have beendeveloped and are being implemented. One current standard in widespreaduse is known as Global System for Mobile Telecommunications (GSM). Thisis considered as a so-called Second Generation mobile radio systemstandard (2G) and was followed by its revision (2.5G). GPRS and EDGE areexamples of 2.5G technologies that offer relatively high speed dataservice on top of (2G) GSM networks. Each one of these standards soughtto improve upon the prior standard with additional features andenhancements. In January 1998, the European Telecommunications StandardInstitute—Special Mobile Group (ETSI SMG) agreed on a radio accessscheme for Third Generation Radio Systems called Universal MobileTelecommunications Systems (UMTS). To further implement the UMTSstandard, the Third Generation Partnership Project (3GPP) was formed inDecember 1998. 3GPP continues to work on a common third generationalmobile radio standard.

A typical UMTS system architecture in accordance with current 3GPPspecifications is depicted in FIG. 1. The UMTS network architectureincludes a Core Network (CN) interconnected with a UMTS TerrestrialRadio Access Network (UTRAN) via an interface known as Iu which isdefined in detail in the current publicly available 3GPP specificationdocuments. The UTRAN is configured to provide wireless telecommunicationservices to users through wireless transmit receive units (WTRUs), knownas User Equipments (UEs) in 3GPP, via a radio interface known as Uu. TheUTRAN has one or more Radio Network Controllers (RNCs) and basestations, known as Node Bs in 3GPP, which collectively provide for thegeographic coverage for wireless communications with UEs. One or moreNode Bs are connected to each RNC via an interface known as Iub in 3GPP.The UTRAN may have several groups of Node Bs connected to differentRNCs; two are shown in the example depicted in FIG. 1. Where more thanone RNC is provided in a UTRAN, inter-RNC communication is performed viaan Iur interface.

Communications external to the network components are performed by theNode Bs on a user level via the Uu interface and the CN on a networklevel via various CN connections to external systems.

In general, the primary function of base stations, such as Node Bs, isto provide a radio connection between the base stations' network and theWTRUs. Typically a base station emits common channel signals allowingnon-connected WTRUs to become synchronized with the base station'stiming. In 3GPP, a Node B performs the physical radio connection withthe UEs. The Node B receives signals over the Iub interface from the RNCthat control the radio signals transmitted by the Node B over the Uuinterface.

A CN is responsible for routing information to its correct destination.For example, the CN may route voice traffic from a UE that is receivedby the UMTS via one of the Node Bs to a public switched telephonenetwork (PSTN) or packet data destined for the Internet. In 3GPP, the CNhas six major components: 1) a serving General Packet Radio Service(GPRS) support node; 2) a gateway GPRS support node; 3) a bordergateway; 4) a visitor location register; 5) a mobile services switchingcenter; and 6) a gateway mobile services switching center. The servingGPRS support node provides access to packet switched domains, such asthe Internet. The gateway GPRS support node is a gateway node forconnections to other networks. All data traffic going to otheroperator's networks or the internet goes through the gateway GPRSsupport node. The border gateway acts as a firewall to prevent attacksby intruders outside the network on subscribers within the networkrealm. The visitor location register is a current serving networks‘copy’ of subscriber data needed to provide services. This informationinitially comes from a database which administers mobile subscribers.The mobile services switching center is in charge of ‘circuit switched’connections from UMTS terminals to the network. The gateway mobileservices switching center implements routing functions required based oncurrent location of subscribers. The gateway mobile services alsoreceives and administers connection requests from subscribers fromexternal networks.

The RNCs generally control internal functions of the UTRAN. The RNCsalso provides intermediary services for communications having a localcomponent via a Uu interface connection with a Node B and an externalservice component via a connection between the CN and an externalsystem, for example overseas calls made from a cell phone in a domesticUMTS.

Typically a RNC oversees multiple base stations, manages radio resourceswithin the geographic area of wireless radio service coverage servicedby the Node Bs and controls the physical radio resources for the Uuinterface. In 3GPP, the Iu interface of an RNC provides two connectionsto the CN: one to a packet switched domain and the other to a circuitswitched domain. Other important functions of the RNCs includeconfidentiality and integrity protection. Background specification datafor such systems are publicly available and continue to be developed.

In general, commercial wireless systems utilize a well defined systemtime frame format for the transmission of wireless communicationsignals. In communication systems such as Third Generation PartnershipProject (3GPP) Time Division Duplex (TDD) and Frequency Division Duplex(FDD) systems, multiple shared and dedicated channels of variable ratedata are combined for transmission. However, irrespective of whether asystem is based on TDD or FDD, received wireless signals must be decodedin accordance with the timeframe structure with which they aretransmitted.

One of the first tasks to be performed in the initiation of a wirelesscommunication is to determine the relative timing of a received signalfor synchronization. In modern systems, there are various levels ofsynchronization, such as, carrier, frequency, code, symbol, frame andnetwork synchronization. At each level, synchronization can be dividedinto two phases: acquisition (initial synchronization) and tracking(fine synchronization).

A typical wireless communication system, such as specified in the 3rdGeneration Partnership Project (3GPP), sends downlink communicationsfrom a base station to one or a plurality of User Equipments (UEs) anduplink communications from UEs to the base station. A receiver withineach UE operates by correlating, or despreading, a received downlinksignal with a known code sequence. The code sequence is synchronized tothe received sequence in order to get the maximal output from thecorrelator.

A receiver may receive time offset copies of a transmitted communicationsignal known as multi-path. In multi-path fading channels, the signalenergy is dispersed over a certain amount of time due to distinct echopaths and scattering. To improve performance, the receiver can estimatethe channel by combining the multi-path copies of the signal. If thereceiver has information about the channel profile, one way of gatheringsignal energy is then to assign several correlator branches to differentecho paths and combine their outputs constructively. This isconventionally done using a structure known as a RAKE receiver.

Conventionally, a RAKE receiver has several “fingers”, one for each echopath. In each finger, a path delay with respect to some reference delay,such as the direct or the earliest received path, must be estimated andtracked throughout the transmission. The estimation of the paths initialposition in time may be obtained by using a multi-path search algorithm.The multi-path search algorithm does an extensive search throughcorrelators to locate paths with a desired chip accuracy. RAKE receiversare able to exploit multi-path propagation to benefit from pathdiversity of transmitted signal. Using more than one path, or ray,increases the signal power available to the receiver. Additionally, itprovides protection against fading since several paths are unlikely tobe subject to a deep fade simultaneously. With suitable combining, thiscan improve the received signal-to-noise ratio, reduce fading and easepower control problems.

During reception, it is not always possible to separate the receivedenergy into components attributable to distinct multipath components.This may happen, for example, if the relative delays of the variousarriving paths are very small compared to the duration of a chip. Suchsituations often arise in indoor and urban communication channels. Theproblem is often referred to as the “Fat Finger Effect.” Accordingly,RAKE receivers have been developed that are capable of identifying theFat fingers, such as the RAKE receiver disclosed in U.S. patentapplication Ser. No. 10/304,894, RECEIVER FOR WIRELESS TELECOMMUNICATIONSTATIONS AND METHOD published as Publication No. US-2003-0157892-A1 onAug. 21, 2003 and owned by the assignee of the present invention. FIG. 2is an illustration of the processing of a received wirelesscommunication signal with a preferred RAKE receiver that includes Fatfinger allocation.

As illustrated in FIG. 2, the received wireless communication system issubject to an initial cell search preprocessing before RAKE fingerallocation. The initial preprocessing identifies reception of a specificsignal sequence such as a pilot sequence or, for example, a preamblesequence of a Random Access Channel (RACH). Various methods of searchingfor and identifying known transmitted signal sequences are know in theart. For example, such methods and apparatus are disclosed in U.S.patent application Ser. No. 10/322,184, APPARATUS AND METHOD OFSEARCHING FOR KNOWN SEQUENCES published as Publication No.US-2003-0161416 on Aug. 28, 2003 and owned by the assignee of thepresent invention.

There are several purposes why a sequence of symbols known to thereceiver might be sent out from a transmitter, for example, channelestimation with respect to timing delay, amplitude and phase such as ina path search; signaling for (slotted) ALOHA multiple access collisiondetection and access granting such as with RACH preamble detection; andsignaling of timing relations and even code group allocations, such asin a cell search.

In cases where lower level signaling is involved, there are usuallyseveral different known sequences that possibly can be sent out, and thesignaling value is dependent on which one is found. Therefore, thesearch has to be performed over all available possible, or relevant,sequences.

The exact receive timing of a known sequence is often not known.Unfortunately, this is exactly the parameter of interest, e.g., for RACHpreamble, if the distance and therefore the propagation latency betweentransmitter and receiver are not known. Additionally, the transmittiming can be completely unknown, such as in cell searching; or thereception of the known sequence could be in different replicas withrespect to timing, amplitude and phase, but these parameters would thenbe of particular interest, such as in path searching.

In general, there is a certain time window when the sequence is expectedto be received, which is constituted by some transmit timingrelationship, or simply the repetition rate if the sequence isrepeatedly sent out on a regular basis. Therefore, on the receive side,a search for the sequence is made within the time window, typically byrepeated correlation of the incoming received signal at consecutiveinstances in time followed by a search of maxima or threshold comparisonin the output signal of the correlator. This operation of correlation atconsecutive time instances can be viewed as finite impulse response(FIR) filtering of the incoming signal using the expected sequence asthe coefficients for the FIR filter. This is in line with the idea ofusing a matched filter for detection.

In a 3GPP system, the known sequences of symbols are transmitted using apulse shaping filter of the root-raised-cosine (RRC) type. On thereceiver side, an RRC-type filter matched to this transmit pulse isused. The combination of both filters, in time domain the convolution,is then of the raised-cosine (RC) type. FIG. 3 shows an impulse responseof an RC filter in time domain, with a filter roll-off factor of 0.22 asused in 3GPP, and being normalized to 1.0 as the maximum amplitude.Amplitude magnitude in dB of the impulse response for the filter of FIG.3, is shown in FIG. 4.

If the transmit and receive timing for a symbol are fully aligned, thereceived signal amplitude is at maximum and for neighboring symbolsspaced at integer multiples of the symbol duration Tc, the receivedsignal is zero. This is one of the essential properties of these typesof filters and is the reason why this type of filter is used in thisapplication.

If the exact symbol timing is not known, and the reception is off bysome timing offset, then the received signal amplitude is not at maximumany more. With the search of a known sequence with unknown timing, theexact symbol timing will typically not be met. Accordingly, this type oferror almost always occurs.

If the search for a known sequence is performed spaced in time at Tc,then the maximum possible timing error is Tc/2, and the amplitudedegradation resulting from this, as shown in FIG. 4, is about 4 dB,which is prohibitive for performance reasons. For a sequence searchperformed spaced at Tc/2, the maximum timing error is Tc/4, and theamplitude degradation 0.94 dB.

In view of the above, performing full correlations at a rate of Tc/2 isthe approach most widely seen in current approaches to the challenge ofa known sequence search with unknown timing. For example, FIG. 5 shows asystem model 10 in which a dirac pulse 12 is applied to a sequence FIRfilter 14 which is applied to a root-raised cosine (RRC) FIR filter 18forming part of the channel 16. At the receiver end, aroot-raised-cosine (RRC) FIR filter 20 receives the transmitted signal,filter 20 being matched to the transmit pulse. The combination of thefilters 18 and 20, function as a raised-cosine (RC) type filter. A knownsequence detector 22 is used in the signal processing chain. After theinterpolation, the post-processing, e.g., maximum search or thresholddetection is performed at stage 22.

Omission of an FIR filter structure from the signal processing chainresults in a search for the known sequence by correlation to eithersuffer from severe performance degradation or to require the alreadymajor chip rate processing complexity to be doubled. For example, FIG. 6shows the “brute force” method wherein the known sequence detector 22includes a correlator finite impulse response (FIR) filter 24, whichreceives the incoming signal at the rate of two samples per chip andprovides its output to the peak search detector 25, likewise operatingat the rate of two samples per chip.

By comparison, the implementation disclosed in Publication No.US-2003-0161416, referenced above and shown in FIG. 7, provides theincoming signal to the sequence correlator FIR filter 24 at the rate ofone sample per chip. Its output, also at one sample per chip, isdirectly applied to a multiplexer 28 as well as an estimation filter 26,which preferably is a four (4)-tap FIR filter. The signal is applied toFIR filter 24 at the rate of one sample per chip and its output,likewise, at the one sample per chip rate, is processed by theestimation FIR filter 26. The multiplexer 28 receives the two signalstreams and alternates passage of these streams to the peaksearch/detector 25 which performs the peak search/detection operation ata rate of two samples per chip. However, even this improved approach isnot optimum with respect to the processing effort.

SUMMARY

A wireless transmit receive unit (WTRU) and methods are used in awireless communication system to process sampled received signals toestablish and/or maintain wireless communications. A selectivelycontrollable coherent accumulation unit produces power delay profiles. Aselectively controllable post processing unit passes threshold qualifiedmagnitude approximation values and PDP positions to a device such as arake receiver to determine receive signal paths.

In one aspect of the invention, various configurations for the postprocessing of produced PDPs are provided. A power delay profile (PDP)production unit produces groups G1-GN of corresponding PDPs each havinga selected number L of sequential elements that have values representingcoherent accumulation of sequential sets of received samples mixed witha known sequence wherein sets of corresponding PDPs are defined by PDPsfrom each group such that for all PDPs of a set of corresponding PDPs,each PDP element is produced based upon coherent accumulation processingusing the same known sequence. A post processing unit is configured toselect less than L/2 PDP elements of each PDP and to store the selectedPDP elements' values and respective PDP position values. The postprocessing unit selectively combines stored PDP values such that thevalues of elements of each PDP of a set of corresponding PDPs that arestored for the same respective PDP position are combined. The postprocessing unit evaluates the combined values for respective PDPpositions against selected thresholds to pass threshold qualifiedcombined values and respective position values for further signalprocessing for use in determining in received signal paths of signalstransmitted with the known sequence with which the respective PDPelements are produced.

The post processing unit can be configured to select N highest values ofeach PDP, where N is >2 and <L/2. Where the PDP element values containin-phase and quadrature components, the post processing unit can beconfigured to selectively combine stored PDP element values by coherentcombination for threshold evaluation. In that case, the post processingunit preferably computes a magnitude approximation value for eachcombined value that is threshold qualified so that the thresholdqualified magnitude approximation values and respective position valuesare utilized in determining received signal paths. As an alternative,the post processing unit can be further configured to compute amagnitude approximation value for each stored PDP element value,noncoherently combine magnitude approximation values corresponding PDPelement values that are coherently combined and separately evaluate bothcoherently and noncoherently combined values against thresholds toqualify values of respective PDP positions for further signal processingin determining received signal paths.

Where the PDP element values processed by the post processing unit aremagnitude approximations of coherent accumulations of sequential sets ofsignal samples, the post processing unit is preferably configured toselectively combine stored PDP element values by noncoherent combinationfor threshold evaluation.

The post processing unit can be configured to select a limited number ofPDP elements from a first group G1 of PDPs, and store those elements'values and respective position values and then store elements' valuesand respective position values of respectively positioned elements fromeach corresponding PDP of a PDP set as each other group of PDPs isprocessed. In that case, a limited number of other elements from PDPswhich do not match any positions of the elements selected from the PDPsof the first group G1 are also selected and stored for thresholdqualification. The post processing unit can be configured to selectelements from the first group G1 PDPs based on selecting the highest Nvalues of PDP elements where N is less than L/4. Alternatively, the postprocessing unit can be configured to select elements from the group G1PDPs by threshold qualification where the threshold is set such thatless than L/4 elements are selected from each of the first group G1PDPs.

A method of processing power delay profiles (PDPs) is provided wheregroups G1-GN of corresponding PDPs each having a selected number L ofsequential elements having values representing coherent accumulation ofsequential sets of received samples mixed with a known sequence whereinsets of corresponding PDPs are defined by PDPs from each group such thatfor all PDPs of a set of corresponding PDPs, each PDP element beingproduced based upon coherent accumulation processing using the sameknown sequence. The method includes selecting less than L/2 PDP elementsof each PDP and storing the selected PDP elements' values and respectivePDP position values. The stored PDP values are selectively combined suchthat the values of elements of each PDP of a set of corresponding PDPsthat are stored for the same respective PDP position are combined. Thecombined values for respective PDP positions are evaluated againstselected thresholds. Threshold qualified combined values and respectiveposition values are passed for further signal processing for use indetermining in received signal paths of signals transmitted with theknown sequence with which the respective PDP elements are produced.Variations of the method are made in accordance with the desiredconfiguration and parameters.

In another aspect of the invention directed to coherent accumulation, anantenna system for receives wireless signals and produces at least onesequential stream of received signal samples at a selected rate. Asequential array of N vector correlators VC[1] to VC[N] are provided,each configured for coherently accumulating L sized sets of sequentialreceived signal samples. The vector correlators are preferably coupledwith the antenna system such that for any given series of N+L−1 samples,S1 to SN+L−1, where the sample S1 is to be a first element of a setprocessed by the first vector correlator VC[1], each vector correlatorVC[i], where i=1 to N, processes respective samples S1 to Si+L−1. Asequence generator is configured to selectively generate known sequencessought to be detected in the received wireless signals. The sequencegenerator is preferably coupled with the vector correlators such that aseach vector correlator VC[i], where i=1 to N, processes a set of Lsequential samples within a series of samples S1 to SN+L−1, a generatedelement Gj of a given known sequence of L generated elements, G0 toGL−1, is mixed with sample Si+j in VC[i] to produce a mixed value thatis coherently accumulated in VC[i]. Vector correlator accumulatorcontrol circuitry is preferably configured to selectively control anaccumulated mixed value output of each vector correlator such that eachvector correlator outputs an accumulated value after accumulating aselected multiple M of sets of L accumulated mixed values. This resultsin power delay profiles (PDPs) of a series of at least N elements E1 toEN being produced where each PDP element Ei represents the coherentaccumulation of M*L mixed values produced by the vector correlatorVC[i], where i=1 to N.

The vector correlator accumulator control circuitry is preferablyconfigured to selectively control an accumulated mixed value output ofeach vector correlator such that each vector correlator outputs aselected number P of accumulated values. In such case, power delayprofiles (PDPs) of a series of N*P elements E1 to EN*P are producedwhere each PDP element Ei+(j*N) represents the coherent accumulation ofM*L mixed values produced by the vector correlator VC[i], where i=1 to Nand j=0 to P−1. The antenna system is preferably configured withmultiple antennas to produce multiple sequential streams of receivedsignal samples at the selected rate. Each vector correlator preferablyincludes a controllable antenna switch device configured to select asample stream from among the multiple sample streams from which toreceive samples for processing by the respective vector correlator.Preferably, antenna switch control circuitry controls the antenna switchdevices such that for any given series of N+L−1 samples, S1 to SN+L−1,where the sample S1 is to be a first element of a set processed by thefirst vector correlator VC[1] received from a particular sample stream,the respective antenna switch device of each vector correlator VC[i],where i=1 to N, is controlled to select the particular sample stream forthe vector correlator VC[i] to process respective samples S1 to Si+L−1received therefrom.

The vector correlators can each be configured with a plurality of naccumulator devices AD1 to ADn. In that case, each respectiveaccumulator device ADj, for j=1 to n, is preferably selectively coupledto the sequence generator to receive elements of a common generatedsequence for mixing with signal samples processed by the respectivevector correlator such that each sample can be processed with ndifferent sequences to produce n accumulations of mixed values. Thisresults in the vector correlator array having the ability toconcurrently produce n PDPs, each corresponding to one of the ndifferent sequences. The sequence generator can includes a scramblingcode generator and n signature code generators. The sequence generatoris then preferably configured with n outputs SGO1 to SGOn such that eachsequence generator output SGOj outputs a different signature/scramblingcode combination sequence of generated elements. Where the vectorcorrelators are each configured with a plurality of n accumulatordevices AD1 to ADn, each respective accumulator device ADj, for j=1 ton, is selectively coupled to the sequence generator to receive elementsof a common generated sequence for mixing with signal samples processedby the respective vector correlator such that each sample can beprocessed with n different sequences to produce n accumulations of mixedvalues. This enables the vector correlator array to concurrently producen PDPs, each corresponding to one of the n different sequences.

Preferably, the vector correlator array operates at a speed that is 48times faster than the selected sampling rate. An interpolator can becoupled with the vector correlators and configured to produce expandedPDPs by increasing the number of elements from P to a desired multipleof P through interpolation. A post processing unit preferably processingthe expanded PDPs by calculating magnitude approximation values ofexpanded PDP values and passing magnitude approximation values andassociated PDP position values that are qualified by the thresholddevice to a RAKE receiver type of device. The WTRU can be configured asa Node B or a UE for use in a Universal Mobile Telecommunications System(UMTS).

A method for processing received wireless signals is provided where atleast one sequential stream of received signal samples at a selectedrate is produced. L sized sets of sequential received signal samples arecoherently accumulated using a sequential array of N vector correlatorsVC[1] to VC[N] such that for any given series of N+L−1 samples, S1 toSN+L−1, where the sample S1 is to be a first element of a set processedby the first vector correlator VC[1], each vector correlator VC[i],where i=1 to N, processes respective samples S1 to Si+L−1. Knownsequences sought to be detected in received wireless signals areselectively generated and mixed, during coherent accumulation, such thatas each vector correlator VC[i], where i=1 to N, processes a set of Lsequential samples within a series of samples S1 to SN+L−1, a generatedelement Gj of a given known sequence of L generated elements, G0 toGL−1, is mixed with sample Si+j in VC[i] to produce a mixed value thatis coherently accumulated in VC[i]. An accumulated mixed value output ofeach vector correlator is selectively controlled such that each vectorcorrelator outputs an accumulated value after accumulating a selectedmultiple M of sets of L accumulated mixed values whereby power delayprofiles (PDPs) of a series of at least N elements E1 to EN are producedwhere each PDP element Ei represents the coherent accumulation of M*Lmixed values produced by the vector correlator VC[i], where i=1 to N.Variations of the method are made in accordance with the desiredconfiguration and parameters.

In a further aspect of the invention the production of power delayprofile (PDP) values is selectively controlled. This is particularlyuseful in path search. A wireless transmit receive unit (WTRU) receiveswireless signals from other WTRUs such that the relative timing of eachwireless signal as received by the WTRU is known and the wirelesssignals are defined by series of a predetermined number J of symbols,SYM(0) to SYM(J−1), transmitted in timeslots of system time frames whereeach symbol has a predetermined bit length B. A power delay profile(PDP) production unit is configured to produces PDPs that each have aselected number L of sequential elements that have values representingcoherent accumulation of sequential sets of a selected number p receivedsamples mixed with a known sequence, where p equals B times for aselected positive integer I, p=B*I. The power delay profile productionunit is preferably configured to selectively produce successive PDPswith respect to received WTRU wireless signals such that when N wirelesssignals are concurrently received, PDPs are produced for respectivewireless signals in order of earliest to latest received signal, WS(0)to WS(N−1), derived from the known timing, starting with a firstearliest received wireless signal WS(0) beginning on the occurrence asymbol SYM(j) with respect to time slot having the receive timing of thefirst wireless signal WS(0) and continuing successively for eachsubsequently received wireless signal WS(n), for n=1 to N−1, beginning,after a time alignment delay based on the known timing of the wirelesssignal WS(n), on the occurrence a symbol SYM((j+(I*n))mod J) withrespect to a time slot having the receive timing of the wireless signalWS(n) whereby the processing of the PDP for the latest received wirelesssignal WS(N−1) begins with a cumulative delay of D chips relative to thestart of the symbol SYM((j+(I*(N−1)))mod J) with respect to a time slothaving the receive timing of the first wireless signal so that the nextPDP produced for the first received wireless signal begins on theoccurrence the symbol SYM(K) with respect to a time slot having thereceive timing of the first wireless signal WS(0), where K is thegreatest integer less than ((j+(I*(N−1))+(D/B))mod J.

Where it is desired to produce PDPs that have values representingcoherent accumulation of sequential sets of received samplesrepresenting J symbols so that p=J*B, the power delay profile productionunit selectively produces successive PDPs with respect to received WTRUwireless signals such that when N wireless signals are concurrentlyreceived, PDPs are produced for respective wireless signals in order ofearliest to latest received signal, WS(0) to WS(N−1), derived from theknown timing, starting with a first earliest received wireless signalWS(0) beginning on the occurrence a symbol SYM(j) with respect to timeslot having the receive timing of the first wireless signal WS(0) andcontinuing successively for each subsequently received wireless signalWS(n), for n=1 to N−1, beginning, after a time alignment delay based onthe known timing of the wireless signal WS(n), on the occurrence asymbol SYM(j) with respect to a time slot having the receive timing ofthe wireless signal WS(n) whereby the processing of the PDP for thelatest received wireless signal WS(N−1) begins with a cumulative delayof D chips relative to the start of the symbol SYM(j) with respect to atime slot having the receive timing of the first wireless signal so thatthe next PDP produced for the first received wireless signal begins onthe occurrence the symbol SYM(K) with respect to a time slot having thereceive timing of the first wireless signal WS(0), where K is thegreatest integer less than (j+(D/B))mod J. In one example, a WTRU isconfigured for use in a Universal Mobile Telecommunications System(UMTS) having system time slot of 2560 chips wherein the power delayprofile (PDP) production unit is configured to produces PDPs forwireless signals received on a pilot channel formatted 10 symbols of 256bits per pilot channel time slot.

A method is provided for controlling power delay profile (PDP)production in a wireless transmit receive unit (WTRU) that receiveswireless signals from other WTRUs such that the relative timing of eachwireless signal as received by the WTRU is known and the wirelesssignals are defined by series of a predetermined number J of symbols,SYM(0) to SYM(J−1), transmitted in timeslots of system time frames whereeach symbol has a predetermined bit length B, where the PDPs each have aselected number L of sequential elements that have values representingcoherent accumulation of sequential sets of a selected number p receivedsamples mixed with a known sequence, where p equals B times for aselected positive integer I, p=B*I. Successive PDPs with respect toreceived WTRU wireless signals are selectively produced such that when Nwireless signals are concurrently received, PDPs are produced forrespective wireless signals in order of earliest to latest receivedsignal, WS(0) to WS(N−1), derived from the known timing, starting with afirst earliest received wireless signal WS(0) beginning on theoccurrence a symbol SYM(j) with respect to time slot having the receivetiming of the first wireless signal WS(0) and continuing successivelyfor each subsequently received wireless signal WS(n), for n=1 to N−1,beginning, after a time alignment delay based on the known timing of thewireless signal WS(n), on the occurrence a symbol SYM((j+(I*n))mod J)with respect to a time slot having the receive timing of the wirelesssignal WS(n) whereby the processing of the PDP for the latest receivedwireless signal WS(N−1) begins with a cumulative delay of D chipsrelative to the start of the symbol SYM((j+(I*(N−1)))mod J) with respectto a time slot having the receive timing of the first wireless signal sothat the next PDP produced for the first received wireless signal beginson the occurrence the symbol SYM(K) with respect to a time slot havingthe receive timing of the first wireless signal WS(0), where K is thegreatest integer less than ((j+(I*(N−1))+(D/B))mod J.

Other objects and advantages will be apparent to those of ordinary skillin the art based upon the following description of presently preferredembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 shows an overview of a system architecture of a conventional UMTSnetwork.

FIG. 2 is a block diagram of an initial Fat finger and RAKE fingerallocation processors of a RAKE receiver.

FIG. 3 is a graph of an impulse response in time domain of an RC filterwith a roll-off factor of 0.22.

FIG. 4 is the amplitude magnitudes in dB of the filter of FIG. 3.

FIG. 5 is a block diagram of a system for achieving timingsynchronization.

FIG. 6 is a block diagram of a sequence detector that uses a “bruteforce” technique for sequence detection for the system of FIG. 5.

FIG. 7 is a block diagram an alternative sequence detector that does notuse a “brute force” technique for sequence detection for the system ofFIG. 5.

FIG. 8 is a block diagram a sequence detection system for a wirelessreceiver made in accordance with the present invention.

FIG. 9 is an expanded block diagram of a portion of the sequencedetection system illustrated in FIG. 8 illustrating a vector correlatorimplementation of coherent accumulation.

FIG. 10 is a further expanded block diagram of a portion of the sequencedetection system illustrated in FIG. 8 illustrating an implementation ofcoherent accumulation for detecting a RACH preamble for a base stationof a 3GPP wireless communication system.

FIG. 11 is an expanded block diagram of a portion of the sequencedetection system illustrated in FIG. 8 illustrating a vector correlatorimplementation of noncoherent accumulation.

FIG. 12 is a processing diagram of preselection by maximum sorting persegment for the sequence detection system where the sequence to bedetected is repetitive and can be divided into segments for detectionanalysis.

FIG. 13 is a processing diagram of timing scheduling for the sequencedetection system for implementing the sorting process in FIG. 12.

FIG. 14 is a processing diagram of preselection by sorting utilizingknown maximum positions for the sequence detection system where thesequence to be detected is repetitive and can be divided into segmentsfor detection analysis.

FIG. 15 is a processing diagram of timing scheduling for the sequencedetection system for implementing the sorting process in FIG. 14.

FIG. 16 is a processing diagram of preselection by threshold comparisonusing known positions for the sequence detection system where thesequence to be detected is repetitive and can be divided into segmentsfor detection analysis.

FIG. 17 is a processing diagram of timing scheduling of sequencedetection for successive path searching with respect to four perfectlysynchronized received signals transmitted by four different WTRUs.

FIG. 18 is a comparative diagram of timing offset of received signalstransmitted by four different WTRUs.

FIG. 19 is a processing diagram of timing scheduling of sequencedetection for successive path searching with respect to the fourreceived signals transmitted by four different WTRUs of FIG. 18 based ontime slot granularity.

FIG. 20 is a processing diagram of timing scheduling of sequencedetection for successive path searching with respect to the fourreceived signals transmitted by four different WTRUs of FIG. 18 based onsymbol granularity.

TABLE OF ACRONYMS 2G Second Generation Mobile Radio System Standard 3GPPThird Generation Partnership Project ARIB Association Of RadioIndustries Businesses ASIC Application Specific Integrated Circuit BLERBlock Error Rate CN Core Network CPCH Common Packet Channel DCHDedicated Channel DL Downlink ETSI SMG European TelecommunicationsStandard Institute - Special Mobile Group FDD Frequency Division DuplexGPRS General Packet Radio Service GSM Global System For MobileTelecommunications HS High Speed HW Hardware MAG Magnitude ApproximationDevice MUX Multiplexer PDP Power Delay Profile PSTN Public SwitchedTelephone Network RACH Random Access Channel RNC Radio NetworkController RRC Radio Resource Control SIR Signal To Interference RatioSW Software TDD Time-Division Duplex TS Time Slot TTI Transmission TimeInterval Tx Transmission UE User Equipment UL Uplink UMTS UniversalMobile Telecommunication System UTRA TDD UMTS terrestrial radio accesstime division duplex UTRAN UMTS terrestrial radio access network VCVector Correlator WTRUs Wireless Transmit Receive Units

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The present invention is described with reference to the drawing figureswherein like numerals represent like elements throughout. The terms basestation, wireless transmit/receive unit (WTRU) and mobile unit are usedin their general sense. The term base station as used herein includes,but is not limited to, a base station, Node-B, site controller, accesspoint, or other interfacing device in a wireless environment thatprovides WTRUs with wireless access to a network with which the basestation is associated.

The term WTRU as used herein includes, but is not limited to, userequipment (UE), mobile station, fixed or mobile subscriber unit, pager,base station or any other type of device capable of operating in awireless environment. WTRUs include personal communication devices, suchas phones, video phones, and Internet ready phones that have networkconnections. In addition, WTRUs include portable personal computingdevices, such as PDAs and notebook computers with wireless modems thathave similar network capabilities. WTRUs that are portable or canotherwise change location are referred to as mobile units.

The present invention is particularly useful when used in conjunctionwith base stations that receive wireless communications from multipleWTRUs, but has broad applicability for WTRUs in general for thedetection of known sequences. For example, the invention can beimplemented in either UEs or Node Bs of the conventional UTMS systemillustrated in FIG. 1 and has particular usefulness for Node B basestations conducting path searching or common uplink physical channeldetection of, for example, FDD RACH or CPCH preambles transmitted withthe format specified by 3GPP TS 25.211 Section 5.2.2.

Referring to FIG. 8, there is shown a Vector Correlator (VC) basedarchitecture 30 for sequence detection in accordance with the presentinvention. When a communication is initiated, the exact time when atransmitted signal sequence reaches a receiver is not known and cansubsequently vary because of the velocity of a mobile WTRU, oscillatoruncertainty and position within a cell service area. The received signalquite often includes more than one copy of a transmitted signal receivedat slightly different times since the radio waves reaching thereceiver's antenna(s) take different paths. A RAKE receiver isconventionally used to combine these copies of received signals toenhance reception capability. Therefore, the base station searcheswithin a certain time window for the arrival of an expected sequence.Generally, a search window is selected of a desired size, such as Lchips in length, where L is selected to be long enough to capture aninitial copy of a signal as well as multipath copies.

Conventionally, front end processing of the received signals isperformed by RF, mixed signal and baseband filtering of signal samples.In the present invention, wireless communication signals are receivedvia one or more antennas ant 1 . . . ant M. The received signals arepreprocessed by sampling at a selected rate. As in the preferredembodiments disclosed in Publication No. US-US-2003-0161416, to avoidrelatively expensive over sampling, sampling is preferably conducted atthe chip rate 1/Tc specified for system transmissions.

After preprocessing the samples can then be correlated to a knownsequence code, i.e. coherent accumulation. For some 3GPP systemtransmissions, for example, correlation is a function of both asequence/signature code of a known length and a scrambling code. Theknown transmitted sequence is often made up of repetitions of a shortersequence or signature. For example, currently a 3GPP FDD RACH preambleis specified as 4096 chips in length consisting of 256 repetitions of a16 bit signature code. There are presently sixteen different signaturecodes specified for RACH preamble transmissions, so that one of those 16bit signatures is selected to create the entire RACH preamble forencoding with a spreading code for a specific transmission. Sixteenspreading codes are normally allotted for each cell of a 3GPP system,but different cells may use different groups of spreading codes.

In a static case, the estimates of the samples can be integrated over acomplete sequence ending up with a maximum increased signal-to-noiseratio (SNR). However that is generally only feasible if the transmittingand receiving WTRUs move relative to each other with only low velocity.If the frequency offset caused by Doppler Effect of up to 250 km/hmovement is taken into account, coherent combining of an entire sequencewill typically not function properly. This is one example of a casewhere it is desirable to partition an overall sequence into smallerequal packages that can be combined noncoherently, NoncoherentAccumulation. For RACH preamble detection, a segment length of 1024chips is preferably selected where each segment represents 64repetitions of the transmitted 16 bit signature code.

In accordance with the present invention, a coherent accumulation unit31 is provided which includes selection of sample streams of receivedsignals from selected antenna sources which are correlated with knownsequences produced by a sequence generator. The sample streams and knownsequences are correlated in a vector correlator array to produce PowerDelay Profiles (PDPs). As explained in detail below, the vectorcorrelator array hardware of the coherent accumulation unit 31 is veryadaptable to produce PDPs under varied sets of parameters. Preferably,an antenna selection unit is included separately for each VectorCorrelator to enable exploitation RX diversity over multiple antennas.Although generally chip alignment of the samples of the same transmittedsignal received on different antennas can be maintained, there may be asignificant phase differential that enhances or lessens the quality ofthe received signal samples for RX processing.

The PDPs produced by the coherent accumulation unit 31 are passed to anInterpolator 32 to increase the chip rate processing by interpolation.Preferably, this is accomplished as described in Publication No.US-2003-0161416 by using an estimation filter 26 as illustrated in FIG.7 to double the chip length which in turn doubles the length of thePDPs.

The expanded PDPs are preferably then passed to a MagnitudeApproximation device 33 (MAG) to approximate the magnitude of theaccumulated samples of each PDP element. Typical with sampling insystems such as those specified by 3GPP, each sample will have at leastan in-phase (I) and a quadrature (Q) component. The resultant PDPelements after coherent accumulation retain I and Q components. Themagnitude approximation performed by the MAG 33 is preferably performedusing the conventional max(I,Q)+0.5 min(I,Q) formulation.

A Noncoherent Accumulation Unit 34 receives the magnitude approximationvalues of the PDP elements and stores them, either in their originalorder or with position information. When complete sets of magnitudeapproximation values of PDP profiles are available, they can be passedthrough a Threshold comparison unit 35 which in turn preferably passesthreshold qualified magnitude approximation and position values to afinger determination component of a RAKE receiver. The PDP elementswhich have sufficient magnitude generally represent the location of thestart of at least one copy of a known transmitted sequence in thereceived wireless signal.

The detected peaks and their positions within the profile are deliveredto RAKE receiver software that preferably starts with a task called ‘FatFinger Detection’. This means that peaks located very close together arenot treated as two separated peaks but are united into one peak to avoidproblems e.g. in assigning Rake fingers. Fat Finger Detection softwareis preferred for both RACH preamble and Path Search sequence detection.

FIG. 9 illustrates a general preferred configuration of a coherentaccumulation unit 40. The coherent accumulation unit 40 includes anarray of associated vector correlators VC[1] . . . VC[N]. In a simplecase, each VC unit produces one value of the PDP for a certain WTRU. Themaximum number of WTRUs that can be processed in parallel and the lengthof the PDP determine the hardware complexity. As explained below,hardware processing speed can be advantageously utilized to producemultiple values with each VC unit to permit a PDP's length to be greaterthan the number of VC units.

Although a single antenna can be used, where multiple antennas Ant 1 . .. Ant M are provided, each vector correlator VC[1] . . . VC[N]preferably includes a respective antenna switch AS[1] . . . AS[N] whichselects a sample stream from among the antennas for processing. Thecoherent accumulation unit 40 includes an input 41 for antenna switchcontrol through which a control signal is sent to the antenna switchesAS[1] . . . AS[N] to switch processing input to a selected antenna'ssamples. Typically a control signal is sent at the start of anaccumulation. Preferably the unit 40 is configured such that the controlsignal from input 41 is directed to the antenna switch AS[1] of thefirst vector correlator VC[1] which is then cascaded sequentially toeach subsequent antenna switch AS[i], i=2 to N, of the respective vectorcorrelator VC[i] with a specified delay, preferably one chip in length.Accordingly, each vector correlator VC[i] preferably commences sequencecorrelation with the ith sample relative to the first sample with whichthe first vector correlator VC[1] commenced sequence correlation. Toimplement the delayed cascading control signal to each subsequentantenna switch AS[i], a delay device z is associated with each precedingantenna switch AS[i−1], such as illustrated for the antenna switch AS[1]of the first vector correlator VC[1].

A sequence generator 42 is provided that generates a known sequence withwhich the sample stream from the selected antenna is correlated in eachvector correlator. The sequence generator is preferably coupled with thevector correlators VC[1] . . . VC[N] via respective mixers 43[1] . . .43[N] to serially mix the generated known sequence with the mixedsamples accumulated in respective accumulation devices 44[1] . . . 44[N]which in turn each produce an accumulated element of the PDP beingproduced. The respective series of samples are mixed with the generatedsequence such that the first generated element is mixed in each vectorcorrelator VC[i] with the ith sample relative to the first sample withwhich the first vector correlator VC[1] commenced sequence correlation,i.e. the first generated element is mixed with the first sample in thefirst vector correlator VC[1] and with the Nth sample in the last vectorcorrelator VC[N]. To implement the delay of generated sequence elementsto each subsequent VC[i], a delay device z is associated with thegenerated sequence element path in each preceding vector correlatorVC[i−1], such as illustrated for the generated sequence element path inthe vector correlator VC[1].

A control input 45 is associated with accumulation devices 44[1] . . .44[N] of the respective vector correlators VC[1] . . . VC[N] to signalthe end of an accumulation at a selected number of samples p to triggerthe output of the respective PDP element by the respective VC. Acorresponding one chip delay device cascades the control signal to eachsubsequent VC[i].

By utilizing hardware devices in the coherent accumulation unit 40 whichoperate at a clock speed greater than the sampling rate, the vectorcorrelators can be used multiple times to produce PDPs having more thanN elements. For example, if the hardware devices in the coherentaccumulation unit 40 operate at a rate 2/Tc that is twice the samplingrate 1/Tc, the sequence generator 42 can be configured to output a firstcopy of a known sequence with respect to every odd element sequentiallyproduced and then a second copy of that known sequence with respect toevery even element sequentially produced after a delay of N evenelements. Thus the first, third and fifth elements outputted from thesequence generator would correspond to the first, second and thirdelements of the first copy of the known sequence and the 2Nth+2, 2Nth+4and 2Nth+6 elements output from the sequence generator would correspondto the first, second and third elements of the second copy of the knownsequence.

In such a case, each sample received from the respective selectedantenna at a rate of 1/Tc is fed twice to the respective mixers 43[1] .. . 43[N] operating at 2/Tc and the accumulator devices 44[1] . . .44[N] track mixings with even and odd generated elements, respectively,with the accumulator devices tracking the even mixings after a delay of2N generated elements. Where p samples are accumulated for each PDPelement, the first vector correlator VC[1] can then process the firstp+N samples from a first antenna to produce the first and Nth+1 elementsof a PDP. The first PDP element being the first p odd accumulated mixedsamples, namely odd mixed samples 1, 3, 5 . . . to 2p+1, and N+1 PDPelement being the even accumulated samples from 2N+2 through 2N+2p.

Alternatively, for such a case where the hardware operates at 2/Tc toprocess 1/Tc received samples, the sequence generator can generate twocopies of the same sequence or two different sequences, where one copyor sequence is generated for odd generated elements and the other copyor different sequence is generated for even generated elements.

In the first case, where two copies of the same sequence are generated,the antenna selectors AS[1] . . . AS[N] can provide alternate copies ofthe each sample from two different antennas so that the VCs process thesamples from one antenna with the odd generated sequence elements toproduce a PDP of that antenna's sampled signals and the VCs process thesamples from other antenna with the even generated sequence elements toproduce a second PDP of the other antenna's sampled signals.

In the second case, where two different sequences are generated, twocopies of each sample can be processed by the VCs to produce a first PDPbased on samples mixed with the odd generated sequence elements thatdefine the first known sequence and to concurrently produce a second PDPbased on samples mixed with the even generated sequence elements thatdefine the second different known sequence. In this way PDPs fromsignals transmitted from two different WTRUs can be concurrentlygenerated; one WTRU that transmitted its signals encoded with the firstknown sequence and the other WTRU that transmitted its signals encodedwith the second known sequence.

More complete examples can be considered for a better understanding ofthe functionality of the coherent accumulation unit 40. Table 1identifies parameters used for functionality and size in theconstruction of the Coherent Accumulation unit.

TABLE 1 Parameters For Coherent Accumulation L Length of search window.K Number of processed delay profiles. N Number of Vector Correlatorunits. M Number of Antennas. c Hardware clock = c * system frequency =c * (Typical value = 3.84 MHz) p Length of coherent accumulation. uNumber of different sequences searched. (FDD RACH: number of scramblingcodes; Path Search: number of WTRUs.)

For simplicity, the following two examples are based on the case of onlyone antenna. In such case, the antenna switches always selects the sameantenna or can be eliminated altogether. For the first example, thehardware is configured for N=10, L=10, M=1, c=1, u=1, p=1024. Thecoherent accumulation unit 40 can then include ten VC units VC[1]-VC[10]running at 1× to produce one delay profile of length ten for one activeWTRU. After 1024 chips are processed, the first VC unit VC[1] producesthe first delay profile value and after 1024+9 chips are processed, thelast VC unit VC[10] produces the last delay profile value and the PDP iscompleted.

In a second example, the hardware is configured for N=10, L=20, M=1,c=2, u=1, p=1024 The coherent accumulation unit 40 can then also includeten VC units VC[1]-VC[10], but running at 2×, to produce one delayprofile of length 20 for one active WTRU. To perform this, two copies ofthe sequence code are queued into the VCs. This can be accomplished, forexample, as discussed above where the first copy is fed into the firstVC unit VC[1] with the odd generated elements, i.e. first, third, fifth,etc. generated elements, and the second copy is fed with a delay oftwenty, i.e.(2*N), elements into the first VC unit VC[1] on the evengenerated elements, i.e. twenty second, twenty fourth, twenty sixth,etc. generated elements. The first VC unit VC[1] then produces the firstPDP value after processing the 1024th sample with the 2047th generatedelement and produces the eleventh PDP value after processing the 1034thsample with the 2068th generated element. Similarly, the last VC unitVC[10] then produces the tenth PDP value after processing the 1033rdsample with the 2047th generated element and produces the twentieth PDPvalue after processing the 1043rd sample with the 2068th generatedelement to complete the PDP of length 20. Thus, ten hardware VC unitsrunning at 2× are used to define twenty virtual VC units running at 1×.

The number of the virtual VC units determines the maximum length of apossible delay profile. In UMTS FDD this is equivalent to the maximumcell radius that can be processed by the coherent accumulation block.The number of the virtual VC units offered by the hardware is theproduct of c*N. The number of system required virtual VC units is theproduct of L*u.

Preferably, for Path Search, the coherent accumulation unit 40 isconfigured with 100 vector correlators VC[1] . . . VC[100] and operatesat 48/Tc to process received signals sampled at 1/Tc. Preferably, thesequence generator is then configured to generate sequences based on 48different scrambling codes in order to concurrently search for sequencestransmitted by up to 48 different WTRUs each using different scramblingcodes. To accomplish this, the sequence generator can be configured suchthat the first element of each different generated sequence is generatedfollowed by each respective sequential element of all the knownsequences before the next sequential element of any of the knownsequences is generated. This permits, for example, the first VC unitVC[1] to process the first signal sample with the first element of eachof the 48 known sequences and to process the ith signal sample with theith element of each the 48 known sequences to produce the first value of48 PDPs, each corresponding to the processing of the received signalwith a different one of the 48 scrambling codes. In this case, thelength of each PDP is 100.

The same hardware configuration can be controlled to produce PDPs oflength 200 where each VC produces two values. This reduces the number ofPDPs that can be concurrently produced from 48 to 24.

In another example configuration, the coherent accumulation unit 40 isconfigured with 64 vector correlators VC[1] . . . VC[64] and operates at48/Tc to process received signals sampled at 1/Tc. For operation, thecoherent accumulation unit 40 is controlled based on cell size per, forexample the following:

-   -   where the cell radius is 40 km for a desired search window of        1024 chips, the sequence generator is then configured to        generate sequences based on 3 scrambling codes in order to        concurrently produce PDPs of length 1024;    -   where the cell radius is 20 km for a desired search window of        512 chips, the sequence generator is then configured to generate        sequences based on 6 scrambling codes in order to concurrently        produce PDPs of length 512;    -   where the cell radius is 10 km for a desired search window of        256 chips, the sequence generator is then configured to generate        sequences based on 12 scrambling codes in order to concurrently        produce PDPs of length 256;    -   where the cell radius is 5 km for a desired search window of 128        chips, the sequence generator is then configured to generate        sequences based on 24 scrambling codes in order to concurrently        produce PDPs of length 128;    -   where the cell radius is 2.5 km for a desired search window of        64 chips, the sequence generator is then configured to generate        sequences based on 48 scrambling codes in order to concurrently        produce PDPs of length 64.

The coherent accumulation unit 40 is particularly useful for wirelesssystem base stations where it is often desirable to detect sequencesfrom multiple concurrent wireless signals. Additionally, the coherentaccumulation unit 40 is very useful for single user WTRUs such as fordetecting multipath signals for path search with respect to acommunication signal received from a base station or other WTRU.

FIG. 10 illustrates a preferred example of a coherent accumulation unit50 configured for 3GPP FDD RACH preamble detection by a base stationwith twenty-two vector correlators VC[1]-VC[22] that operates at 48/Tcto process received signals sampled at 1/Tc. As explained above, thispermits a variety of PDPs that have a length which is a multiple of 22to be readily produced. The coherent accumulation unit 50 is preferablyconfigured to produce PDPs with a length in accordance with the cellsize serviced by the base station based on the parameters set forth inthe Table 2. Accordingly, where for example the PDP size is selected as88, each of the VCs produce four elements of each PDP.

TABLE 2 Preferred 3GPP FDD RACH PDP lengths Distance Anti/Code (km)Profile Length Comb. .086 22 48 1.72 44 24 3.44 88 12 6.87 176 6 13.75352 3 41.25 1056 1

As with the general embodiment illustrated in FIG. 9, each vectorcorrelator VC[i] has an associated antenna switch AS[i] and, with theexception of the first VC unit VC[1], operates with a one chip delaywith respect to each respective predecessor VC unit VC[i−1]. Thecoherent accumulation unit 50 similarly includes an input 51 for antennaswitch control signals operates with a one chip delay with respect tothe respective antenna switches. In the coherent accumulation unit 50,each vector correlator is modified to contain a number of accumulatordevices equivalent to the number of signature codes available. In thecase of current FDD RACH specifications, sixteen signature codes areavailable, so each vector correlator VC[i] preferably includes sixteenaccumulator devices 54[i, 1]-54[i, 16], respectively.

A sequence generator 52 for generating RACH scrambling codes isprovided. The sequence generator 52 is associated with each of sixteensignature code generators 52[s 1]-52[s 16]. Preferably, each signaturecode generator 52[sj] repeatedly generates one of the sixteen specified16 bit signatures used to form the 16 different RACH preambles that arepermitted. The output of each signature code generator 52[sj] is mixedwith one or more scrambling sequences generated by the sequencegenerator 52 to provide the known sequence elements to a respectiveaccumulator device 54[1,j] of the first vector correlator VC[1] and isthen cascaded with a chip delay to the corresponding accumulator device54[i,j] of each subsequent vector correlator VC[i].

Where the PDP length is set at 22, the sequence generator 52 canadvantageously be configured to generate 48 RACH scrambling codes.Although currently 3GPP specifications designate sixteen scramblingcodes be available for a FDD RACH preamble transmission, different setsof scrambling codes for different cells can be provided. Accordingly,the capacity to generated 48 different scrambling codes, enables a basestation to detect all signature/scrambling code combinations for FDDRACH preambles concurrently for three different cells within a 3GPPsystem where different scrambling code sets are used within eachdifferent cell.

In such a case, the mixing with a “jth” signature generated by therespective signature code generator 52[sj] passes 48 differentlyscrambled copies of the jth signature sequence to the respectiveaccumulator device 54[1,j] of the first vector correlator VC[1] whichgenerates the first PDP element of 48 PDPs, each corresponding to adifferently scrambled version of the jth signature sequence. Arespective set of 48 PDPs is generated for each of the sixteen differentRACH signature code preambles. Accordingly, in such a configuration, thecoherent accumulation unit 50 will detect a RACH preamble transmitted inthe observed window for any WTRU RACH preamble transmission based on anyof the 48 scrambling codes in combination with any of the 16 permittedsignature sequences.

Using j for signature code and i for scrambling code to denote theproduced PDPs as PDP[j,i], if the PDP identified by PDP[12,17] containsnon-noise values, PDP[12,17] then reflects reception of a RACH preambletransmitted by a WTRU using the 12th specified signature sequence andthe 17th scrambling code. If only a small number of WTRUs aretransmitting RACH preambles, only a small number of the produced PDPswill contain non-noise values, those being the PDPs corresponding tosignature/scrambling code combinations used by the transmitting WTRUs.

Preferably the coherent accumulation unit 50 receives signal samplesfrom one or more pairs of antennas such as pair Ant_1 a, Ant_1 b throughAnt_6 a, Ant_6 b as illustrated in FIG. 10. Since RACH preambles consistof repetitive segments, the coherent accumulation unit 50 can beconfigured to produce PDPs for RACH preamble segments instead of PDPsfor entire preamble sequences.

The configuration for the coherent accumulation unit 50 can be based ondividing 4096 chip RACH preambles into four 1024 chip segments forcoherent accumulation while exploiting antenna diversity. In such acase, one preferred example is to switch the antenna signal samplesource for each segment between signals received from two antennas of anantenna pair in producing length 22 PDPs. Accordingly, antenna Ant_1 acan provide the first 1024 samples to VC[1] to produce the first PDPvalues of the PDPs corresponding to each of the signature/scramblingcode combinations for the first RACH preamble segment. The antennaswitch AS[1] then switches to antenna Ant_1 b to provide the samples1025 through 2048 to VC[1] to produce the first PDP values of the PDPscorresponding to each of the signature/scrambling code combinations forthe second RACH preamble segment. The antenna switch AS[1] then switchesback to antenna Ant_1 a to provide the samples 2049 through 3072 toVC[1] to produce the first PDP values of the PDPs corresponding to eachof the signature/scrambling code combinations for the third RACHpreamble segment. The antenna switch AS[1] finally switches back toantenna Ant_1 a to provide the samples 3073 through 4096 to VC[1] toproduce the first PDP values of the PDPs corresponding to each of thesignature/scrambling code combinations for the fourth RACH preamblesegment. The antenna switching is delayed one chip for each subsequentVC so that VC[22] processes signal chips 22 to 1043 and 2070 to 3091from antenna Ant_1 a and chips 1044 to 2069 and 3092 to 4115 fromantenna Ant_1 b/to produce the last PDP values of PDPs corresponding theeach of the signature/scrambling code combinations for the four RACHpreamble segments. FIG. 15 reflects a timeline for such VC processing, Lbeing equal to 22 in the above example.

After PDP values are produced by the coherent accumulation unit, theyare preferably passed to the interpolator 32 which in turn passesinterpolated values with the original PDP values to the MAG 33. Althoughthe coherent accumulation over p samples generally takes p chips of timeto produce each PDP value, the values are outputted from the coherentaccumulation unit for each PDP at the rate of the delay in processing byeach successive VC. As explained above, that delay is preferably onechip so that the PDP values for each PDP are produced at a 1/Tc rate.Accordingly, the interpolator 32 preferably doubles the chip rate foreach PDP to 2/Tc when providing the interpolated values which define anexpanded PDP that is processed by the MAG 33.

Where multiple PDPs are concurrently produced, the interpolator can beconfigured to operate at a higher speed or multiple interpolators can beprovided to process different ones of the PDPs concurrently produced.For example, where coherent accumulation unit 50 is configured toconcurrently produce PDPs of length 22 for each of 16 signature code and48 scrambling code combinations, sixteen interpolators can be provided,each operating to output expanded PDPs at a collective rate of 96/Tc foran overall effective output rate of 1536/Tc. To process such acollective output, the MAG 33 can be divided into thirty two MAGsubunits each operating at 48/Tc to perform magnitude approximation ofthe values for the respective expanded PDPs produced via theinterpolation unit 32.

In the preferred embodiment as illustrated in FIG. 8, after magnitudeapproximation in the MAG 33, the values produced for each of theexpanded PDPs are passed to the noncoherent accumulation unit 34. Asbest seen in FIG. 11, the noncoherent accumulation unit 34 preferablyincludes K round robin structures 62[1]-62[K] of length 2L so that eachround robin structure can store an entire expanded set of magnitudeapproximation values for one PDP. A control input 65 is provided tocontrol a de-multiplexing device 66 such that respective values of eachrespective expanded PDP set received from the MAG 33 are directed to arespective round robin structure 62[1]-62[K]. The respective sets ofexpanded PDP values are then directed from the round robin structures tothe threshold comparison unit 35 which passes magnitude and positionvalues of respective expanded PDPs to the RAKE finger detection unit 36of a RAKE receiver. Preferably, only a selected number of highest valueswith their positions are passed through the threshold comparison unit 35to the RAKE finger detection unit 36. This type of pure noncoherentprocessing does not impair SNR performance and is relativelyinexpensive.

From time to time new PDPs may be produced. A control signal thenchooses the respective round-robin structure to update the new PDP. ForRACH Preamble Detection the number of round-robin structures ispreferably fixed at 16*u. For Path Search, the number is selected basedon whether the PDPs are to be delivered on a time frame basis or on atime slot basis, a time frame basis being preferred. The noncoherentaccumulation unit 34 can be configured such that the output of the roundrobins is selectively controlled to combine related PDPs. For example,PDPs for different RACH segments of the same signature/scrambling codecombination can be directed to threshold comparison unit 35 concurrentprocessing by the RAKE receiver. Similarly, where the sequence detectionhardware is configured for Path Search on a time frame basis, thenoncoherent accumulation unit 34 is preferably configured to permit PDPcombinations segment wise for intra-slot combining and also PDPcombinations slot-wise for inter-slot combining in addition to PDPcombinations antenna-wise for antenna diversity combining. The same verysimple structure of a pool of round-robin units permits such versatilityof combinations since all of the relevant PDPs to be combined arereadily accessible from the collection of round-robin units.

The size of the memory required for the round robins of the noncoherentaccumulation unit 34 is a direct function of the number K of PDPs to bestored and the PDP size L. As K and L increase, the memory requirementscan become prohibitive.

For RACH preamble detection, the preferred size of the memory is closeto the border of acceptance, but the simplicity of the structuredescribed above supports the viability of the configuration reflected inFIG. 11 for such an application. However, RACH preamble detection is notthe only application for the sequence searcher.

For example, the current 3GPP specifications for the Common PacketChannel (CPCH) based on packet channel technology specifies thetransmission of a preamble that is very similar the preamble specifiedfor the RACH. However, for the CPCH the number of possible scramblingcodes is increased to 64. This in turn increases the necessary memory toimplement the noncoherent accumulation unit 34 as illustrated in FIG.11. In cases where such a simple configuration becomes memoryprohibitive, it is preferred to implement algorithms that enable areduction of that memory in the processing of produced PDPs.

FIGS. 12, 14, and 16 provide three alternatives that provide alternateprocessing in place of the noncoherent accumulation unit 34 illustratedin FIG. 11. For explanatory purposes, the three alternatives aredescribed based on a RACH preamble with the length of 4096 chips, whichis also used for the CPCH case, where the preamble is partitioned into 4segments each of 1024 chips in length. PDP elements for each segment areproduced by coherently combining chip samples over 1024 chips, i.e.p=1024, in a coherent accumulator unit such as unit 50 illustrated inFIG. 10. The produced PDPs that represent the four segments of aparticular transmitted sequence are then combined coherently and/ornoncoherently. The combining of the four segments is called postprocessing.

The alternatives to reduce the memory are based on preselectionalgorithms. The three different methods of post processing reflected inFIGS. 12, 14, and 16 can be characterized, respectively, as:

-   -   Preselection by maximum sorting;    -   Preselection by sorting utilizing known maximum positions; and    -   Preselection by threshold comparison using known positions.        For post processing preselection by sorting, a scalable sorter        is preferably provided to implement these methods.

For the example of RACH preamble detection, a search is made over up to48 scrambling codes, 16 signatures and a search window of length varyingfrom 22 to 1024. The coherent accumulation unit can creates largematrices A_(j), j=1 to 4, of PDP values for each respective segment toconsider all signature/scrambling code combinations. In lieu ofproviding the memory to store a complete set of values produced for thesegment matrices Aj, j=1 to 4, in the round robin structures of thenoncoherent accumulation unit 34, preselection can be advantageouslyemployed. This is feasible since only very few elements of a limitednumber of PDPs profile will represent received preamble transmissions.The rest of the PDP values represent accumulated noise.

The combined PDPs are compared against thresholds. If a value is above aselected threshold a Preamble is considered detected as starting at therespective position of the PDP value within the PDP. The thresholds arepreferably chosen such that a to False Alarm and Missed Detection rateof 10⁻³ is reached. False alarm happens if a preamble is considereddetected when no preamble was sent. Missed detection happens if apreamble is not detected when it was sent. The conventional thresholdsemployed for the threshold detector 35 serve as a reference with respectto False Alarm and Missed Detection rate for the preselectionalternatives.

Preselection By Maximum Sorting

Referring to FIGS. 12, an overall diagram of the process is providedfrom the production of the expanded PDPs with interpolated values, whichincrease the set size of the PDP values to 2L each, to the passing ofthreshold qualified PDP values and associated positions to the RAKEfinger control of a RAKE receiver. A preferred distribution betweenhardware and software implementation of the various functions isindicated by the slight shading of the functions preferred to beimplemented in hardware.

MAG functionality is optionally implemented in either hardware orsoftware at one of the three illustrated locations, MAG¹, MAG², MAG³,depending upon whether coherent and/or noncoherent combination of PDPvalues is desired. The combining of PDP values by adding their complexcomponents prior to transformation into magnitude approximation valuesrepresents coherent combining such as when the MAG functions occur atposition MAG¹. The combining of PDP values by adding their magnitudeapproximation values represents noncoherent combining such as when theMAG functions occur at position MAG³. When the MAG functions occur atposition MAG², both coherent and noncoherent combining can beimplemented to pass both raw complex combined values and magnitudeapproximation values for each respective PDP position for thresholdevaluation. In such case, preferably, if either the complex combinedvalue or the magnitude approximation value exceeds a respectivethreshold, the magnitude approximation value and associated positiondata passes through the threshold comparison to the RAKE finger control.

Assuming the MAG functionality is located at MAG¹, the processingpreselection by Maximum Sorting proceeds as set forth in FIG. 12 withthe timing set forth in FIG. 13 as explained in the followingparagraphs.

The first segment PDPs are generated and interpolated, represented byA1, and those values are passed through a sorting device to find Nmaximum values per PDP and to then store the N complex values andrespective position values in a memory R1.

The second segment PDPs are generated and interpolated, represented byA2, starting concurrently with the sorting of the A1 values. The A2values are passed through a sorting device to find N maximum values perPDP and to then store the N complex values and respective positionvalues in a memory R2.

The third segment PDPs are generated and interpolated, represented byA3, starting concurrently with the sorting of the A2 values. The A3values are passed through a sorting device to find N maximum values perPDP and to then store the N complex values and respective positionvalues in a memory R3.

The fourth segment PDPs are generated and interpolated, represented byA4, starting concurrently with the sorting of the A3 values. The A4values are passed through a sorting device to find N maximum values perPDP and to then store the N complex values and respective positionvalues in a memory R4.

The number of elements per PDP processed above is intended to includeadditional elements created through interpolation and can be referred toas L′. Preferably interpolation doubles the number of elements per PDPso that for PDPs originally produced with L elements, L′=2*L. The numberN of maximum values is always selected to less than half of L′, but ispreferably substantially less than that number. For example, where asearch window is 1024 chips which results in L′=2048 due to doubling byinterpolation, N is preferably 100 so that the highest 100 PDP valuesare selected from each PDP of A1, A2, A3 and A4.

Tables 3 and 4 provide representative hardware requirements for thescalable sorter and memories R1-R4 for implementing the above process.

TABLE 3 Sorter hardware Sorter: Hardware in kgates 1 sorter 2.443Overall Control 10 sum (16sig, 2 sorting-cycles, even/odd) 2 * 2 * 16 *2.443 + 10 = 166

TABLE 4 Sorter memory per segment Sorter: Memory per segment in bits L =64, N = 20, 20 * 3 * 16 * 48 * 16 = 737280 16 bits/word, i/q/position

Thereafter a processor 75 a is provided to access the memories R1-R4 tocoherently combine the stored values of PDP sets of corresponding PDPsof the four segments, i.e. each PDP set defined by one PDP from each ofA1, A2, A3 and A4, to perform the following steps:

-   -   Find all positions of Rj, j=1 to 4, that occur twice per PDP        set. Combine the found complex amplitudes coherently and store        the results and the related positions in a software construct        S2.    -   Find all positions of Rj, j=1 to 4, that occur three times per        PDP set. Combine the found complex amplitudes coherently and        store the results and the related positions in a software        construct S3.    -   Find all positions per PDP set that occur in each of the four        sets Rj, j=1 to 4. Combine the found complex amplitudes        coherently and store the results and the related positions in a        software construct S4.        In stead of coherent combining, noncoherent combing and/or a        combination of the two is performed based on the alternate MAG        locations MAG², MAG³ as discussed above.

Processing continues with a comparison against respective thresholds K1,K2, K3 for each PDP set's values passed to S2, S3 and S4. If a candidateis above a threshold its position is stored and the Preamble isdetected. Thresholds are different for S2, S3 and S4 due the number ofvalues combined. Thresholds are also different for coherent andnoncoherent metrics based upon their characteristic values, but areselected to achieve a desired False Alarm and Missed Detection rate.

Preselection By Sorting Utilizing Known Maximum Positions.

Referring to FIGS. 14, an overall diagram of the process is providedfrom the production magnitude approximation values by the MAG based onthe expanded PDPs with interpolated values to the passing of thresholdqualified expanded PDP magnitude approximation values and associatedpositions to the RAKE finger control of a RAKE receiver. A preferreddistribution between hardware and software implementation of the variousfunctions is indicated by the slight shading of the functions preferredto be implemented in hardware.

MAG functionality can optionally be implemented in a different location,depending upon whether coherent and/or noncoherent combination ofexpanded PDP values is desired. FIG. 14 illustrates a preferredembodiment where noncoherent combining of expanded PDP values is done byadding their magnitude approximation values. Accordingly, thepreselection by sorting utilizing known maximum positions preferablyproceeds as set forth in FIG. 14 with the timing set forth in FIG. 15.

The first segment PDPs are generated, interpolated and have theirmagnitudes approximated to produce the matrix of expanded PDP magnitudeapproximation values represented by A1. Those values are preferablypassed through a sorting device to find N1 highest maximum values perPDP that are passed to a register R1′_(val) in ranked order withrespective position values passed to a corresponding position registerR1′_(pos). The N1 highest maximum values are then resorted in accordancewith position order and the resorted N1 maximum values per PDP arestored in a memory R1 _(val) with respective position values passed to acorresponding position memory R1 _(pos). A distribution deviceassociated with the R1 _(val) and R1 _(pos) memories selectively passesthe N1 maximum magnitude and position values of a respective firstsegment PDP to a software construct combining device S4 whencorresponding position values for corresponding second, third and fourthsegment PDPs have been stored as discussed below.

The second segment PDPs are generated, interpolated and have theirmagnitudes approximated to produce the matrix of expanded PDP magnitudevalues represented by A2. Those values are first passed through aposition matching device to extract magnitude and position values, persecond segment PDP, corresponding to the positions of the N1 highestmaximum values of each corresponding first segment PDP which are thenstored in a memory R21. The remaining second segment PDP values,represented by A2′, are passed through a sorting device to find N2highest maximum values per PDP that are passed to a register R2′_(val)in ranked order with respective position values passed to acorresponding position register R2′_(pos). The N2 highest maximum valuesare then resorted in accordance with position order and the resorted N2maximum values per PDP are stored in a memory R2 _(val) with respectiveposition values passed to a corresponding position memory R2 _(pos). Adistribution device associated with the R2 _(val) and R2 _(pos) memoriesselectively passes the N2 maximum magnitude and position values of arespective second segment PDP to a software construct combining deviceS3 when corresponding position values for corresponding third and fourthsegment PDPs have been stored as discussed below.

The third segment PDPs are generated, interpolated and have theirmagnitudes approximated to produce the matrix of expanded PDP magnitudevalues represented by A3. Those values are first passed through aposition matching device to extract magnitude and position values, perthird segment PDP, corresponding to the positions of the N1 highestmaximum values of each corresponding first segment PDP which are thenstored in a memory R31 and corresponding to the positions of the N2highest maximum values of each corresponding second segment PDP whichare then stored in a memory R32. The remaining third segment PDP values,represented by A3′, are passed through a sorting device to find N3highest maximum values per PDP that are passed to a register R3′_(val)in ranked order with respective position values passed to acorresponding position register R3′_(pos). The N3 highest maximum valuesare then resorted in accordance with position order and the resorted N3maximum values per PDP are stored in a memory R3 _(val) with respectiveposition values passed to a corresponding position memory R3 _(pos). Adistribution device associated with the R3 _(val) and R3 _(pos) memoriesselectively passes the N3 maximum magnitude and position values of arespective second segment PDP to a software construct combining deviceS2 when corresponding position values for corresponding fourth segmentPDPs have been stored as discussed below.

The fourth segment PDPs are generated, interpolated and have theirmagnitudes approximated to produce the matrix of expanded PDP magnitudevalues represented by A4. Those values are passed through a positionmatching device to extract magnitude and position values, per fourthsegment PDP, corresponding to:

-   -   the positions of the N1 highest maximum values of each        corresponding first segment PDP which are then stored in a        memory R41,    -   the positions of the N2 highest maximum values of each        corresponding second segment PDP which are then stored in a        memory R42, and    -   the positions of the N3 highest maximum values of each        corresponding second segment PDP which are then stored in a        memory R43.

Once N1 elements of a fourth segment PDP are stored in the R41 memory, adistribution device associated with the R41 memory, in conjunction withsimilar distribution devices associated respectively with the R31, R21memories and in conjunction with the distribution device associated withthe R1 _(val) and R1 _(pos) memories, can selectively pass a completeset of values to the software construct combining device S4. Such acomplete set of values is constituted of the magnitude and positionvalues that correspond to the N1 positions of N1 maximum first segmentPDP values for each of corresponding first, second, third and fourthsegment PDPs. The software construct S4 then passes a combined magnitudevalue with a respective position value to an associated thresholdcomparison unit where the combined magnitude values are compared againsta threshold K1. The combined magnitude values that exceed the K1threshold are then passed with their respective position values to theRAKE finger control of a RAKE receiver.

Once N2 elements of a fourth segment PDP are stored in the R42 memory, adistribution device associated with the R42 memory, in conjunction witha similar distribution device associated with the R32 memory and inconjunction with the distribution device associated with the R2 _(val)and R2 _(pos) memories, can selectively pass a complete set of values tothe software construct combining device S3. Such a complete set ofvalues is constituted of the magnitude and position values thatcorrespond to the N2 positions of N2 maximum second segment PDP valuesfor each of corresponding second, third and fourth segment PDPs. Thesoftware construct S3 then passes a combined magnitude value with arespective position value to an associated threshold comparison unitwhere the combined magnitude values are compared against a threshold K2.The combined magnitude values that exceed the K2 threshold are thenpassed with their respective position values to the RAKE finger controlof a RAKE receiver.

Once N3 elements of a fourth segment PDP are stored in the R43 memory, adistribution device associated with the R43 memory, in conjunction withthe distribution device associated with the R3 _(val) and R3 _(pos)memories, can selectively pass a complete set of values to the softwareconstruct combining device S2. Such a complete set of values isconstituted of the magnitude and position values that correspond to theN3 positions of N3 maximum third segment PDP values for each ofcorresponding third and fourth segment PDPs. The software construct S2then passes a combined magnitude value with a respective position valueto an associated threshold comparison unit where the combined magnitudevalues are compared against a threshold K3. The combined magnitudevalues that exceed the K3 threshold are then passed with theirrespective position values to the RAKE finger control of a RAKEreceiver. The respective thresholds K1, K2, K3 are different for S2, S3and S4 due the number of values combined, but are selected to achieve adesired False Alarm and Missed Detection rate.

The number of elements per PDP processed above is intended to includeadditional elements created through interpolation and can be referred toas L′. Preferably interpolation doubles the number of elements per PDPso that for PDPs originally produced with L elements, L′=2*L. The totalnumber N1+N2+N3 of maximum values is always selected to less than halfof L′, but is preferably substantially less than that number. Forexample, where a search window is 1024 chips which results in L′=2048due to doubling by interpolation, N1 is preferably 90 that the highest90 PDP values are selected from each PDP of A1; N2 is preferably 80 thatthe highest 80 PDP values are selected from each PDP of A2′; and N3 ispreferably 50 that the highest 50 PDP values are selected from each PDPof A3′.

Preselection By Threshold Comparison Utilizing Known Positions.

Referring to FIGS. 16, an overall diagram of the process is providedfrom the production magnitude approximation values by the MAG based onthe expanded PDPs with interpolated values to the passing of thresholdqualified expanded PDP magnitude approximation values and associatedpositions to the RAKE finger control of a RAKE receiver. A preferreddistribution between hardware and software implementation of the variousfunctions is indicated by the slight shading of the functions preferredto be implemented in hardware.

MAG functionality can optionally be implemented in a different location,depending upon whether coherent and/or noncoherent combination ofexpanded PDP values is desired. FIG. 16 illustrates a preferredembodiment where noncoherent combining of expanded PDP values is done byadding their magnitude approximation values. Accordingly, thepreselection by sorting utilizing known maximum positions preferablyproceeds as set forth in FIG. 16.

The first segment PDPs are generated, interpolated and have theirmagnitudes approximated to produce the matrix of expanded PDP magnitudevalues represented by A1. Those values are preferably passed through athreshold comparison unit where the magnitude values are comparedagainst a threshold K4. The magnitude values that exceed the K4threshold are then passed to a memory R1 _(val) with respective positionvalues passed to a corresponding position memory R₁ _(pos). Adistribution device associated with the R1 _(val) and R1 _(pos) memoriesselectively passes K4 qualified magnitude and position values of arespective first segment PDP to a software construct combining device S4when corresponding position values for corresponding second, third andfourth segment PDPs have been stored as discussed below.

The second segment PDPs are generated, interpolated and have theirmagnitudes approximated to produce the matrix of expanded PDP magnitudevalues represented by A2. Those values are first passed through aposition matching device to extract magnitude and position values, persecond segment PDP, corresponding to the positions of the K4 qualifiedmagnitude values of each corresponding first segment PDP which are thenstored in a memory R21. The remaining second segment PDP values,represented by A2′, are passed through a threshold comparison unit wherethe magnitude values are compared against a threshold K5. The magnitudevalues that exceed the K5 threshold are then passed to a memory R2_(val) with respective position values passed to a correspondingposition memory R2 _(pos). A distribution device associated with the R2_(val) and R2 _(pos) memories selectively passes the K5 qualifiedmagnitude and position values of a respective second segment PDP to asoftware construct combining device S3 when corresponding positionvalues for corresponding third and fourth segment PDPs have been storedas discussed below.

The third segment PDPs are generated, interpolated and have theirmagnitudes approximated to produce the matrix of expanded PDP magnitudevalues represented by A3. Those values are first passed through aposition matching device to extract magnitude and position values, perthird segment PDP, corresponding to the positions of the K4 qualifiedmagnitude values of each corresponding first segment PDP which are thenstored in a memory R31 and corresponding to the positions of the K5qualified magnitude values of each corresponding second segment PDPwhich are then stored in a memory R32. The remaining third segment PDPvalues, represented by A3′, are passed through a threshold comparisonunit where the magnitude values are compared against a threshold K6. Themagnitude values that exceed the K6 threshold are then passed to amemory R3 _(val) with respective position values passed to acorresponding position memory R3 _(pos). A distribution deviceassociated with the R3 _(val) and R3 _(pos) memories selectively passesthe K6 qualified magnitude and position values of a respective secondsegment PDP to a software construct combining device S2 whencorresponding position values for corresponding fourth segment PDPs havebeen stored as discussed below.

The fourth segment PDPs are generated, interpolated and have theirmagnitudes approximated to produce the matrix of expanded PDP magnitudevalues represented by A4. Those values are passed through a positionmatching device to extract magnitude and position values, per fourthsegment PDP, corresponding to:

-   -   the positions of the K4 qualified magnitude values of each        corresponding first segment PDP which are then stored in a        memory R41,    -   the positions of the K5 qualified magnitude values of each        corresponding second segment PDP which are then stored in a        memory R42, and    -   the positions of the K6 qualified magnitude values of each        corresponding second segment PDP which are then stored in a        memory R43.

Once all elements corresponding to first segment K4 qualified magnitudevalue positions of a fourth segment PDP are stored in the R41 memory, adistribution device associated with the R41 memory, in conjunction withsimilar distribution devices associated respectively with the R31, R21memories and in conjunction with the distribution device associated withthe R1 _(val) and R1 _(pos) memories, can selectively pass a completeset of values to the software construct combining device S4. Such acomplete set of values is constituted of the magnitude and positionvalues that correspond to the first segment K4 qualified magnitude valuepositions for each of corresponding first, second, third and fourthsegment PDPs. The software construct S4 then passes a combined magnitudevalue with a respective position value to an associated thresholdcomparison unit where the combined magnitude values are compared againsta threshold K1. The combined magnitude values that exceed the K1threshold are then passed with their respective position values to theRAKE finger control of a RAKE receiver.

Once all elements corresponding to second segment K5 qualified magnitudevalue positions of a fourth segment PDP are stored in the R42 memory, adistribution device associated with the R42 memory, in conjunction witha similar distribution device associated with the R32 memory and inconjunction with the distribution device associated with the R2 _(val)and R2 _(pos) memories, can selectively pass a complete set of values tothe software construct combining device S3. Such a complete set ofvalues is constituted of the magnitude and position values thatcorrespond to the second segment K5 qualified magnitude value positionsfor each of corresponding second, third and fourth segment PDPs. Thesoftware construct S3 then passes a combined magnitude value with arespective position value to an associated threshold comparison unitwhere the combined magnitude values are compared against a threshold K2.The combined magnitude values that exceed the K2 threshold are thenpassed with their respective position values to the RAKE finger controlof a RAKE receiver.

Once all elements corresponding to third segment K6 qualified magnitudevalue positions of a fourth segment PDP are stored in the R43 memory, adistribution device associated with the R43 memory, in conjunction withthe distribution device associated with the R3 _(val) and R3 _(pos)memories, can selectively pass a complete set of values to the softwareconstruct combining device S2. Such a complete set of values isconstituted of the magnitude and position values that correspond to thethird segment K6 qualified magnitude value positions for each ofcorresponding third and fourth segment PDPs. The software construct S2then passes a combined magnitude value with a respective position valueto an associated threshold comparison unit where the combined magnitudevalues are compared against a threshold K3. The combined magnitudevalues that exceed the K3 threshold are then passed with theirrespective position values to the RAKE finger control of a RAKEreceiver.

The number of elements per PDP processed above is intended to includeadditional elements created through interpolation and can be referred toas L′. Preferably interpolation doubles the number of elements per PDPso that for PDPs originally produced with L elements, L′=2*L. The K4, K5and K6 thresholds are always selected so that the total number of PDPelements per PDP passed to the memories is less than half of L′, but ispreferably substantially less than that number. The K4, K5 and K6thresholds can all be the same value and preferably set with valueslower than the K1 threshold. The respective thresholds K1, K2, K3 aredifferent for S2, S3 and S4 due the number of values combined.Collectively the thresholds are selected to achieve a desired FalseAlarm and Missed Detection rate.

The post processing discussed above is not only applicable for the caseof selectively combing PDPs of preamble segments, such as 3GPP RACH andCPCH preambles, but can also be used to combine PDP updates such as aregenerated for Path Search. In a 3GPP setting, it is not uncommon thatthe detection of the power delay profile PDP of a certain UE-Node Bconnection and the related finger assignment of the Rake Receiver maytake up to one radio frame (10 ms) which is long enough to completelychange the fading conditions that were valid for the PDP estimation.Therefore, it is desirous that Path Search is designed in that way that(unless for very low velocities) all connections from UEs to a Node Bare detected and kept until it is decided that the path connection doesnot exist anymore. By averaging the PDP results over a certain timeperiod, a path con be maintained even if a particular PDP updatereflects its disappearance as long as it is redetected within a certaintime period.

Generally, noncoherent accumulation increases signal to noise ratio(SNR) and is not restricted by fading conditions and thus is desirableover a relatively long time period. The length of time is generallyrestricted by the update rate of the allocated paths at the Rakereceiver. This update rate can be once per system frame and, in such asituation, the duration of noncoherent accumulation is preferably not belonger than one time frame.

Averaging of the candidate profiles over a certain time period can avoidlosing a valid path where momentary detection thereof does not occur.This time period depends on relative velocity and mobility environment.A reasonable value is 5 frames or 50 ms.

A 3GPP Node B is typically equipped to receive transmissions with twoantennas. The sequence detection system configured for Path Search canreadily exploit the RX diversity of dual antenna reception. Dual receiveantennas are generally uncorrelated with respect to fast fading, butcorrelated with respect to slow fading. In other words: the detectedlocation of the signal paths is the same on both antennas but theamplitude of the paths is different. This can be exploited bynoncoherent combining of PDPs produced based on respective signalsreceived from the two antennas to result in a noise reduction and infading mitigation.

Selective Path Search Control

One objective of a Path Searcher is to identify new signal paths andtrack previously detected signal paths with respect to their timelymovement. The timely movement is caused by the frequency offset seenfrom the Node B. This frequency offset is the sum of the Doppler Offsetintroduced by a mobile WTRU's velocity and the frequency offsetintroduced by its oscillators.

As noted above, some or all path connections from a WTRU to a basestation can suffer from fast fading. Depending on the velocity of themobile WTRU, path connections can seem to disappear caused byinterference, but then appear again. Degradation by fading does not meanthat the connection does not exist; it can reflect that the path ismomentarily not recognizable because of phase interference. A path mayoften reappear after a mobile WTRU has moved on the order of half awavelength.

In order to facilitate path search, each transmitting WTRU with which acommunication has been established can, for example, continuallybroadcast a pilot sequence on a pilot channel with a unique spreadingcode relative to the other transmitting WTRUs with which communicationhas been established. One known transmission format for a pilot sequenceis to repetitively transmit the pilot symbol in timeslots of a systemtimeframe where each time slot is defined by 10 symbols and each symbolconsists of 256 chips. A unique scrambling code is used to encode thepilot signals for each transmitting WTRU communicating with the basestation so it is possible coherently combine all of the chips of anentire timeslot based on vector correlation with the respectivescrambling codes even if not all the symbols that are transmitted arethe same.

The sequence detection system 30 can be used to generate PDPs for eachcommunication being received from a different WTRU in a serial manner bychanging the generated sequence to reflect different spreading codes forthe generation of successive PDPs. Where for example, concurrentcommunications are being conducted with four WTRUs, PDPs for each can besuccessively generated and then the process repeated to provide updatedPDP values.

One approach for generating successive PDPs for received signals fromdifferent WTRUs is to begin coherent accumulation for each successivePDP at the start of a time slot. FIG. 17 illustrates the case ofrepeatedly processing successive PDPs of length L for four WTRUs, WTRU1, WTRU 2, WTRU 3, WTRU 4 where the received signals happen to beprecisely synchronized and the transmissions are made in time slots often 256 chip symbols per time slot so that the time slots have a lengthof 2560. Since the received signals are synchronized, the beginning ofeach time slot of every signal is precisely aligned with the end of theprevious time slot signals for all of the WTRUs. Accordingly, in thisexample, there is a delay of precisely four PDP time slots betweencompletion of update PDPs for a particular WTRU's signal. This isreflected in FIG. 17 where one PDP for WTRU 1 is completed at the end oftime slot 1 plus L chips and the next PDP for WTRU 1 is completed at theend of time slot 5 plus L chips.

Precise synchronization of received signals, however, is difficult toachieve and maintain in practice, particularly where the transmittingWTRUs are mobile. For example, a significant characteristic of a 3GPPFDD system is that UE signals reaching a Node B are not synchronized.Therefore each UE-Node B connection has a different timing.

Generally the timing of at least one relatively strong path for eachdifferent received transmission is known from which a transmission'srelative time frame start position is identified. Accordingly, thereceived signals can be ordered for processing on a priority ofreception basis with knowledge of the amount of timing offset betweeneach different signal. FIG. 18 illustrates how received signals for fourWTRUs may be offset in time. WTRU 1 being illustrated as the firstreceived signal of the four signals and WTRU 4 being illustrated as thelast received signal of the four signals. Since the WTRU receivedsignals are not synchronized, in scheduling the PDP processing timingadjustment delays are required.

FIG. 19 illustrates the case of repeatedly processing successive PDPs oflength L for four WTRUs, WTRU 1, WTRU 2, WTRU 3, WTRU 4 of FIG. 18 wherethe received signals are not synchronized and the transmissions are madein time slots of ten 256 chip symbols per time slot so that the timeslots have a length of 2560. Since the received signals are notsynchronized, there is a timing delay equal to the timing requiredbefore beginning of each successive PDP generation. For example, thegeneration of the PDP for WTRU 2 starts at the beginning of WTRU 2'stime slot 2 which has a timing offset from the end of WTRU 1's time slot1 so the start of the processing of the WTRU 2 PDP is delayed by thatamount of time. Similarly, the generation of the PDP for WTRU 3 startsat the beginning of WTRU 3's time slot 3 which has a timing offset fromthe end of WTRU 2's time slot 2 so the start of the processing of theWTRU 3 PDP is delayed by that amount of time. Likewise, the generationof the PDP for WTRU 4 starts at the beginning of WTRU 4's time slot 4which has a timing offset from the end of WTRU 3's time slot 3 so thestart of the processing of the WTRU 4 PDP is delayed by that amount oftime.

At the end of WTRU 4's time slot 4, the next PDP for WTRU 1 is scheduledfor generation. However, at that time a cumulative delay of D chips hasoccurred with respect to the timing of the WTRU 1 signal. Accordingly,processing of the next PDP for the WTRU 1 received signal can not startat the beginning of WTRU 1's slot 5, but is delayed until at thebeginning of WTRU 1's slot 6, a delay of 2560-D chips. Since all PDPprocessing in this example starts at the beginning of a signal's timeslot, the delay characteristic can be referred to as time slotgranularity.

The inventors have recognized that in certain circumstances equivalentPDPs can be produced which are not limited to time slot transmissions.In particular, the inventors have recognized the for typical pilotsignals transmitted by 3GPP specified WTRUs, accumulation of samplesover an equal number of successive symbols of a signal sample willresult in an equivalent PDP usable to Path Search updates. Accordingly,the coherent accumulator unit 31 of the sequence detector 30 can beadvantageously configured to produce successive PDPs for nonsynchronized received signals of different WTRUs with only a symbolbased granularity delay. Accumulation values for the produced PDPs arestill based on 2560 chip accumulations for each PDP element, but thestart of processing of each PDP is only required to be relative to thestart of a transmitted symbol, not the start of a time slot.

FIG. 20 illustrates the case of repeatedly processing successive PDPs oflength L for four WTRUs, WTRU 1, WTRU 2, WTRU 3, WTRU 4 of FIG. 18 wherethe received signals are not synchronized and the transmissions are madein time slots of ten 256 chip symbols per time slot so that the timeslots have a length of 2560. Since the received signals are notsynchronized, there is a timing delay equal to the timing requiredbefore beginning of each successive PDP generation. For example, thegeneration of the PDP for WTRU 2 starts at the beginning of WTRU 2'stime slot 2 which has a timing offset from the end of WTRU 1's time slot1 so the start of the processing of the WTRU 2 PDP is delayed by thatamount of time. Similarly, the generation of the PDP for WTRU 3 startsat the beginning of WTRU 3's time slot 3 which has a timing offset fromthe end of WTRU 2's time slot 2 so the start of the processing of theWTRU 3 PDP is delayed by that amount of time. Likewise, the generationof the PDP for WTRU 4 starts at the beginning of WTRU 4's time slot 4which has a timing offset from the end of WTRU 3's time slot 3 so thestart of the processing of the WTRU 4 PDP is delayed by that amount oftime.

At the end of WTRU 4's time slot 4, the next PDP for WTRU 1 is scheduledfor generation. As with the processing based on time slot granularityillustrated in FIG. 19, at that time a cumulative delay of D chips hasoccurred with respect to the timing of the WTRU 1 signal. However, byprocessing on a symbol granularity basis, the processing of the next PDPfor the WTRU 1 received signal need not start at the beginning of WTRU1's next occurring timeslot, i.e. WTRU 1's slot 6, but is scheduled tocommence at WTRU 1's next occurring symbol, a delay of less than 256which is significantly lees than the 2560-D chip delay in the case oftime slot granularity. Arbitrarily denoting the symbol as J, FIG. 20illustrates that the accumulation of PDP values is with respect to theJth Symbol of WTRU 1's Slot 5 through the (J−1)th Symbol of WTRU 1'sSlot 5. The production of the next PDPs for the other WTRUs similarlycommence with the Jth Symbol of a respective time slot.

In general, PDP production with the sequence detector 30 is applicablebased on symbol granularity where a series of J symbols, SYM(0) toSYM(J−1), having a bit size B are transmitted per time slot and Isymbols are coherently accumulated for each PDP element. PDP productionis then preferably controlled to selectively produce successive PDPswith respect to received WTRU wireless signals such that when N pilotsignals are concurrently received, PDPs are produced for respectivewireless signals, WS(0) to WS(N−1), in order of earliest to latestreceived signal derived from the known timing. Starting with a firstearliest received wireless signal WS(0), a PDP is produced beginning onthe occurrence a symbol SYM(j) with respect to time slot having thereceive timing of the first wireless signal WS(0). PDP productioncontinues successively for each subsequently received wireless signal,WS(n) for n=1 to N−1, beginning, after a time alignment delay based onthe known timing of the signal WS(n), on the occurrence a symbolSYM((j+(I*n))mod J) with respect to a time slot having the receivetiming of the wireless signal WS(n) whereby the processing of the PDPfor the latest received wireless signal WS(N−1) begins with a cumulativedelay of D chips relative to the start of the symbolSYM((j+(I*(N−1)))mod J) with respect to a time slot having the receivetiming of the first wireless signal WS(0). The next PDP produced for thefirst received wireless signal WS(0) begins on the occurrence a symbolSYM(K) with respect to a time slot having the receive timing of thefirst wireless signal WS(0), where K is the greatest integer less than((j+(I*(N−1))+(D/B)) mod J.

The example of FIG. 20 illustrates the case where the coherentaccumulation for PDP elements is performed over the number of symbols inone time slot, i.e. I=J. In such a case, PDP production continuessuccessively for each subsequently received wireless signal, WS(n) forn=1 to N−1, begins, after a time alignment delay based on the knowntiming of the signal WS(n), on the occurrence a symbol SYM(j) withrespect to a time slot having the receive timing of the wireless signalWS(n) and the next PDP produced for the first received wireless signalWS(0) begins on the occurrence a symbol SYM(K) with respect to a timeslot having the receive timing of the first wireless signal WS(0), whereK is the greatest integer less than (j+(D/B))mod J.

The reduction in processing delay is even more significant since it iscumulative over time. Each time a WTRU 1 PDP is to be generated asimilar delay of less then 256 chips is encountered using Symbolgranularity scheduling in contrast to the 2560-D chip delay for timeslot granularity processing.

The scheduling on a symbol basis and instead of a slot basis is notproduce exactly the same result in processing a received 3GPP signal ona pilot channel since 3GPP specifications permit the transmission ofmore than one type of 256 bit symbol. However, the difference isrelatively minimal and compensation can be made by doing morenoncoherent accumulations compared to a scheduling on slot basis.

Scheduling the coherent accumulation unit 40 to produce PDPs for thesame received signal at different times allows time diversity for thenon-coherent accumulation. This is particularly useful for improvingperformance by countering various path fading characteristics ofreceived signals. This can be referred to as non-pseudo-randomscheduling of the vector correlator which can be compared with thepseudo-random approach such as disclosed in U.S. patent application Ser.No. 10/304,403 filed Nov. 26, 2002 entitled RECEIVER FOR WIRELESSTELECOMMUNICATION STATIONS AND METHOD published as Publication No.US-2003-0152167-A1 on Aug. 14, 2003 and owned by the assignee of thepresent invention. However, non-pseudo-random scheduling of the vectorcorrelator provides essentially equivalent performance at a lowerimplementation cost.

Preferably, the components of FIGS. 8-12, 14, and 16 are implemented onan single integrated circuit, such as an application specific integratedcircuit (ASIC). However, the components may also be readily implementedon multiple separate integrated circuits. Elements indicated as having apreferred to be implementation in software may be supplied as firmwareon such ASICs.

The foregoing description makes references to 3GPP and 3GPP FDD systemsas examples only and not as a limitation. The invention is applicable toother systems of wireless communication where known sequences aredetected by WTRU receivers. Other variations and modificationsconsistent with the invention will be recognized by those of ordinaryskill in the art.

1. A method for use in wireless communication, the method comprising:processing a plurality of power delay profiles (PDPs) that each includea plurality of PDP elements; selecting less than half of the PDPelements of each PDP; selectively combining the selected PDP elementsbased on a position of the PDP elements; and qualifying the combined PDPelements for further signal processing to determine a received signalpath of a signal associated with the PDPs.
 2. The method of claim 1,wherein the selecting includes selecting PDP elements having a highestvalue among the PDP elements in each PDP.
 3. The method of claim 1,wherein the selectively combining includes performing coherentcombination; further comprising: computing a magnitude approximation foreach combined PDP element.
 4. The method of claim 1, wherein theselectively combining includes coherently combining the PDP elements,and noncoherently combining magnitude approximation values correspondingto the coherently combined PDP elements; and the qualifying includesseparately evaluating the coherently combined PDP elements and thenoncoherently combined PDP elements.
 5. The method of claim 1, whereinthe selectively combining includes noncoherently combining the PDPelements where each PDP element includes a magnitude approximation of acoherent accumulation of sequential sets of signal samples.
 6. Themethod of claim 1, wherein the selecting includes: selecting a PDPelement from a first group of PDPs; selecting a corresponding PDPelement from each of a plurality of other groups of PDP elements; andselecting a non-corresponding PDP element.
 7. The method of claim 6,wherein the selecting a PDP element from a first group includesselecting a PDP element having a highest value.
 8. The method of claim6, wherein the selecting a PDP element from a first group includesselecting such that less than one-quarter of the elements of a PDP areselected from each PDP in the first group.
 9. The method of claim 1further comprising: interpolating groups of PDPs to provide acorresponding number of at least twice as many PDP elements at a clockspeed of at least twice a sampling rate of a PDP production unit.